1. Field of the Disclosure
The present disclosure relates generally to image forming devices and more particularly to an insert molded bearing for a rotatable component of an image forming device.
2. Description of the Related Art
Various rotatable components of an electrophotographic image forming device require an applied voltage to function properly. One example of such a component that requires an applied voltage is a charge roll that charges the surface of a photoconductive drum. Intermittent or total loss of electrical contact to the charge roll can result in severe print detects visible to the user. The electrical path to the charge roll is typically provided through bearings that support the axial ends of a shaft of the charge roll. One approach is to use an electrically conductive plastic bearing connected to a metal compression spring that contacts an electrically conductive contact pad. However, conductive plastics are highly sensitive to the molding process used to form the bearing. If the conductive agent is not evenly and properly dispersed throughout the part, conductive plastics can have variable and overall high resistance values that can lead to print defects. Creepage and clearance concerns must also be addressed when using conductive plastic due to the relatively high voltage nature of charging. A typical area of concern is the proximity of the conductive plastic charge roll bearing to other components, such as the photoconductive drum. Insufficient distance can result in arcing between the charge roll bearing and the photoconductive drum, causing a print defect referred to as black line shorts.
Another approach is to provide electrical contact to the charge roll through a metal bearing that supports the axial end of the shaft of the charge roll and that is snap-fitted or slid into a. nonconductive plastic shell that encapsulates the metal bearing in order to shield the metal bearing from the photoconductive drum. This approach reduces the risk of arcing between the charge roll bearing and the photoconductive drum but also increases the cost and complexity of the bearing assembly in comparison with an electrically conductive plastic bearing.
Instead of providing electrical contact to the charge roll through the charge roll bearing, another approach is to provide electrical contact to the shaft of the charge roll independent of the charge roll bearing, such as through a cantilevered sheet metal spring that touches the end of the shaft of the charge roll. This approach reduces the risk of arcing between the charge roll and the photoconductive drum. However, connections to the end of the shaft of the charge roll typically require additional space compared to the use of a conductive charge roll bearing, which conflicts with consumer preferences for smaller image forming devices.
Accordingly, an improved bearing capable of providing electrical contact to a rotatable component, such as a charge roll, is desired.